Tension control (TC) bolts – twist-off

How it works

A TC bolt has a domed head and a splined end. The shear wrench holds the spline and turns the nut; when the bolt tension reaches the calibrated value the spline twists off at its groove. A missing spline is a visible, permanent record that the bolt was tensioned.

TC bolts save time on large bolted structures – multi-storey frames, bridges and long-span roofs – and remove impact-wrench noise from the site.

Grades

Installation notes

• Pre-installation verification of each lot in a tension calibrator
• Keep bolts in their sealed containers – lubrication controls the tension
• Snug all bolts first, then twist off in a pattern from the stiffest part of the joint
• Do not re-use bolts that have been tensioned